Method of making grid assemblies



Sept. 1952 E. E. BORLAND EI'AL memos OF MAKING GRID ASSEMBLIES 2 SHEETS-SHEET 1 Filed March 22, 1945 FIG. I

FIG. 3

FIG. 6

INVENTORS EILEEN E. BORLAND. GARRET A. HOBART"! CASIMIR Z. NAWROCKI & HENRY V. NEHER ATTORNEY Sept. 16, 1952 E. E. BORLAND ETAL METHOD OF MAKING GRID ASSEMBLIES 2 SI-EETS- SHEET' 2 Filed March 22, 1945 FIG. IO

IN VEN TORS EILEEN E. BORLAND. GARRET A. HOBART Ill CASIMIR Z. NAWROCKI & HENRY V. NEHER ATTORNEY Patented Sept. 16, 1952 Eileen .E. Borland, Cambridge, I Garret A. Ho-

bart, 3d, and Casimir Z. Nawrocki, Boston, and

' 1 Henry V. Neher, Arlington, Mass., assignors, by mesne assignments, to the United States of America as represented by the Secretary of War I ApplicationMarch 22, 1945, Serial No. 584,225

This invention relatesgenerally to electrical apparatus and more particularly to fine wire grids for vacuum tubes and to methods for making such grids. g

The use of ultra-high. frequencies introduced the problem of designing vacuu'm tubes having transit times small compared to the period of oscillation. This problem resulted in the placing of the grid very close to the cathode. Such close spacing, if relatively large wires are used, causes variations in the transit times of emitted'electrons.

The construction of fine wire grids presents various problems such as the accurate'positioning of the fine wires on small grid supports. The problem of obtaining propertension on these fine grid wires, along with proper-spacing, is' one which cannot be solved by previous methods. Because of the close inter-electrode. spacing in tubes as well as because of the design of the tubes themselves, the thickness oi material used in the grid supports and support holders is often limited.

One of the objects of this invention is to provide grids of accurately spaced fine wires to eliminate the above mentioned variations of transit times of emitted electrons. Another object of this invention is'to' provide methods of manufacturing such fine wire grids.

For a better understanding of the invention together with other objects and features thereof, reference is had to the following detailed de.-

'scription taken-in connection with the accompanying drawings in which: 1

Fig. 1 is a plan view of a grid support with grid wires attached;

Fig.12 is a perspective view of a grid winding holder with guide,ifeed' spool and brake;

Fig. 3 is a plan view of a small grid support with grid-wires attached; H

' Fig. 4 is a' plan view of a convoluted grid support holder with a completed grid supportinserted;

Fig. 5 is a cross sectional view of grid support in Fig. 4 shown through axis X-X;

Fig. 6 is aplan view of a grid support holder for holding single grid supports;

Fig. 7 is a cross. sectional view through axis XIXI of grid support holder shown in Fig. 6;

Fig. 8 is a plan view of a grid support with grid wires tightened by a convolute die method;

I Claims. (Cl. 29-2517) Fig. 9 is aperspective view of a grid winding holder used'for winding single or double grids; and

Fig. 10 isa cross sectional view of a cylindrical die which is used to press convolutes ingrid supports for tightening grid wires.

Referring now morepartioularly to Fig. 1, a fine vwire grid construction is shown comprising grid wires attached to and supported by grid support 2|. 1

One method of manufacturing the grid shown in Fig. 1 is shown, in Fig. 2 in which grid wire 22 is wound on a ring 23 that is made of wire with two opposite sides flattened to provide straight sections. on which the grid wire 22 is wound. .Small. nickel tabs 24 are spot welded to a straight section of ring 23 to provide a means for holding thewire to prevent unraveling. The ring 23 is clamped in a holder 25 which is rotated by a lathe. The ring 23 isstretched when clamped in the holder 25, so that the distance between thestraight portions of the ring 23 may be shortened by any desired amount which might be required to tighten the grid wires 20 after completing the winding. A slotted why 26, mounted on the lathe carriage, is used as a guide for grid Wire 22. The grid. wire 22 is fed from a spool 21 which is mounted on a shaft 28. Also mounted on shaft 28' is a wheel 29 which is braked by a brush 30 to provide the necessary tension for winding the grid wire 22.

Grid support 2 I, shown in Fig. 1, is inserted between the two layers of grid Wires 20 wound on ring 23. The wires 20 are then gold soldered in a hydrogen atmosphere to the grid support 2|. The grid support 2! ,withattached wires 20 is then cut-away from the winding ring 23 and the grid wires are cut ofi at the outside rim of the grid support. i

InFig. 3 the grid support 32 is made of tungsten and is of no larger size than is physically necessary for supporting the grid'wire durin manufacture and use. Nickel tabs 33 are spot welded to the support to hold the grid wire ends.

This grid may be produced by holding support 32 ina convenient clamp holder and Winding it in the manner shown in Fig. 2. No method of tightening is used in making. grids with tungsten discs with the grid wire wound directly thereon. The tungsten disc has the same expansion as the tungsten grid wires and the winding tension has to be relied upon to provide sufflcient tension to hold the grid wires straight.

Fig. 4 shows a composite type of grid construction which has in combination a small double grid, such as shown in Fig. 3, soldered to a molybdenum convoluted support holder 34. The convoluted support holder 34 is used where a rigid support is needed for small grids and where space will allow the use of convoluted construction. Fig. 5 shows a cross sectional view of Fig. 4 through axis. XX.

Fig. 6. shows arnons-convolutedgricl holder-36 which may be used where thickness is a limiting factor. Fig. '7 is a cross section view of Fig. 6 through axis XI-XI. It consists of a supporting ring which has a small offset3lpressed near the inner rim. The offset 31 should be of such dimensions that the grid support will lit-into it. The grid support should be soldered-in and, if a thinner construction is desired...they1ip formedby the offset may then be turned-off in a lathe. 1 In the event a double grid is used and a single'grid is desired, one set of grid wires may :then. be removed from the grid support.

In Fig. 8 there is shown a preferred grid construction comprising support 39 having approximately the shape of a disc with-two opposite peripheral notches 40 and a central aperture covered by grid wires 4|. A convolute 42 in support-39 and wires 4| surrounds theaperture.

'Fig. 9 illustrates a preferred methodof manu-' facturing grids.

Holder 44 clamps one end of the'dumbb'ell type winding supports, and clamp 45 clamps the other end. The molybdenum grid supports 46 and 41 sandwich a separator 48 of any material, suchas a ceramic: or -tungsten coated with graphite, that will not adhere to gold. "Two nickel tabs 49' are spot welded to one of the forms for fasteningthe ends of grid wires 50. The grid is wound in the same manner as wasthe ring 23 described in Fig. 2., The wound supports "are then placed in a hydrogenatmosphere .ajndhthe grid wires soldered to the modybdenurngrid discs 46 and 4! with-gold.- The grid 'wires'50 may then be cut at the .outer edges. of the grid supports and the singlegrids 4.6 and 41 obtained.

Since it is often desirable to 'tighten grid wires to keep the wires straight and in position, a'die shown in Fig. maybe used." The bottom die 52 has acircularwell of size to accommodate a grid assembly 45. A circular groov'e'53 is .cut .in the-bottom withits inside diameter slightly larger than the grid aperture. Top die.54 fitsinto' the base well and has a circularridg'eiiliof the same diameter as groove53n A center plugg5fi, slightly longer than the top; die, holds the grid ,flat while the top die presses a. convoluteon the grid. A pad1'5'l of lead or other material is used to distribute the pressure from a. press evenly to the. die

'54 and plunger .56. .The. convolute :thus made enlarges the grid 'aperture. .and therebytightens the grid wiresby. an amountproportional totheir lengths. By pressing a convolute inthe grid, the rid may be wound with. only sufiicientten's-ion to keep the .wires straightandinposition.

The. size anddepth of theconvolute can. be varied to produce the .desired tighteningof the grid wires. It. ierdesirable; to.;,place the-:gridJaS- sembly 46 in well. 5.2 with. the gridiwires :down when making the convolute. ..Sinc.ethe wires are of. t. .1gSten,-,.they would rapidly dull the convolute ridge 55 on the die if .they faced upwardly. It is'to be understood that the above described grids and grid supports may be made from m .theapertureof the grid ,diso. -The dumbbell type of. grid disc isypreferred since it conserves on grid wire. The method of feeding the wire while winding the discs is subject to many variations. When winding grids, aslotted ruby grid wire guide 1 is. preferred to other. materials since it it has good wearing qualities.

'1 While therehasbeen described what is at present consideredto-be the preferred embodiments of this: -inyention, it will be obvious to those .skilledinthaart-that various changes and modifications maybe made therein without departing from the scopeof the invention as set forth in the rappended claims.

The invention claimed is:

1. The method oimaking a grid assembly comprising taking asupport having a central aperture therein andplacing ajplurality. of wires ,onsaid support, the wires overlying and extending :beyond on. each side of. saidaperture, permanently conductively. bonding. theends of each wire to theesupport and deforming simultaneously the supportandwires intermediate the. attached ends and .the aperture. to tension, the wires.

2.. .The method otmaking agrid assembly comprisings the steps of-increasing .the distance between the ends of a resilient winding frame to diminish the-distance between its sides, winding wire-substantially laterally about said frame to form agrid of a. plurality ofv substantially parallelstrands: of wire :spanning said sides, allowing the: framex-tocresume its normal shape, thereby pu'ttingssaid.strands'of wire of said grid under tension, placing asupport having a central aperture therein-oversaidwires so that the wires lie across the aperture-and extend beyond on each side ofsaid" aperture, permanently, conductively bonding the wire, to the .support near each edge, cutting away-L the. wires extendingbeyond the edgesof. thessupport and deforming simultaneously theedupport and wires intermediate the attached ends, and-the aperture to tension the wires.

3. The method-of making a grid assembly comprising; the following :1 steps, j clamping together twoametallicrgridzsupports.having a central aperture in each i-support with a separator between the two supports, winding a wire about the clamped members to'form a plurality of wires lying acrossand extending beyond the apertures on each side of each support,permanently, conductively bonding the wires. to each support near eachedge' oieaohsupport, cutting away the wires extending beyond the edges-of each support, and deforming simultaneously the support and wires intermediate the attachedends and the aperture to tension the wires.

--IEILEEN1E. 'BORLAND. LazGARRET A. HOBART, 3D. CASIMIR Z. NAWROCKI. LUHENRY V. NEHER.

1' (Re erencespn following page) REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Hadaway Dec. 14, 1915 Eldred June 27, 1916 Neal Nov. 7,1922 Trimble Aug. 21, 1923 Smythe June 14, 1932 Robinson May 8,1934 Clark May 7, 1935 Klinkert May 21, 1935 Kershaw June 11,1935 Morrison Mar. 31, 1936 Number Number Name Date Little Oct. 18, 1938 Anderson Feb. 7, 1939 Riley Oct. 3, 1939 Schade Oct. 10, 1939 Krahl Dec. 26, 1939 Joyner Aug. 29, 1944 Eitel et a1. Oct. 3, 1944 Bingley Mar; 26, 1946 ,FOREIGN PATENTS Country Date Great Britain Apr. 13, 1933 Germany Nov. 26, 1936 Germany Apr. 8, 1933 

